Re: [foxboro] AB Int 30B
- From: kirk.d.carver@xxxxxxxxxxxxxx
- To: foxboro@xxxxxxxxxxxxx
- Date: Thu, 17 Oct 2002 14:40:28 -0500
Just to add to Corey's statements, I talked with one of our control
engineers back at my old facility. He had this to put in:
1. Each ABSCAN block should reside in it's own individual compound, and
should be the first block in that compound list.
2. All the MCIN, CIN, MCOUT, AOUT, AIN, and MAIN blocks following the
ABSCAN block must have the same period and phase as the ABSCAN block.
3. Make the PLC addresses you're communicating to be contiguous, and
ordered by direction of communication: all the data from the PLC to I/A
should be in one block, and all the data from I/A to the PLC should be in
another.
4. If you want to communicate with a lot of PLCs, one kludge to consider
is buying a very small PLC to act as a multiplexer. The I/A speaks only to
this one multiplexer PLC. The multiplexer PLC uses the Allen-Bradley
native "MSG" instruction to do peer-to-peer communications between itself
and all the other PLCs. Peer-to-peer messaging on a "Data Highway Plus" is
actually very quick;
----------------------
Kirk Carver
ExxonMobil Development
Ph: 281-654-4881
Fax: 281-654-4223
GP6--358
Internet Address: kirk.d.carver@xxxxxxxxxxxxxx
"Corey R Clingo"
<clingoc@basf-corp To: foxboro@xxxxxxxxxxxxx
.com> cc:
Sent by: Subject: Re: [foxboro] AB Int
30B
foxboro-bounce@fre
elists.org
10/17/02 11:47 AM
Please respond to
foxboro
Someone correct me if I'm wrong, but I think the documented max # of PLCs
is 7. There is also a limit on total # of words/second from all PLCs (350
I think for an I30)
However, I/O loading problems on Integrator 30s is unfortunately something
we've experienced. The I30s are not very powerful boxes, and can be rather
flaky as well (in our experience). One thing to look at is how many ABSCAN
blocks do you have? One thing we found out is to try to make the PLC
registers as contiguous as possible, and use as few ABSCAN blocks as
possible. Apparently the overhead of an ABSCAN block in building the scan
request to the PLC is fairly significant, so for example 5 ABSCAN blocks of
10 words apiece will use much more I/O time than one ABSCAN block of 50
words. Also, you can look at more obvious stuff, like scan rate of the
blocks, etc.
I don't know about the second port, as we've never used both of them.
Maybe that is because it is for redundant links only, but I don't know for
sure.
Corey Clingo
BASF Corp
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| | "Dale Gillis" |
| | <doctorg@xxxxxxxx|
| | tico.ca> |
| | Sent by: |
| | foxboro-bounce@fr|
| | eelists.org |
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| | |
| | 10/17/2002 12:27 |
| | PM |
| | Please respond to|
| | foxboro |
| | |
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| To: foxboro
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| Subject: [foxboro] AB Int 30B
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Anybody know or have an idea of how many PLC's (AB PLC 5/40) you can look
at with just one Integrator 30B through an AB KF2 card. I currently have
just 2 PLC's on the one Integrator and One KF2 card and only scanning 38
words for input and 20 words for output per PLC and the station loading
screen goes up to 90% loaded in the i/o. Can you hook up more than one KF2
to the same Integrator 30B processor (that is are the other serial ports
available on the elevator) or should I be looking at some other way to
accomplish this? I would like to have at least 7 PLC's hooked up
eventually.
Regards,
Dale Gillis
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